Bugfix/bacnet real endian simplify (#89)

* Remove dependence on endian define

* Make use of existing big_endian function if BACNET_BIG_ENDIAN is not defined

* Add efficient endian macro option if available

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/bacdcode.h

@@ -182,6 +182,11 @@ extern "C" {
         uint8_t * apdu,
         uint8_t tag_number,
         float value);
+    BACNET_STACK_EXPORT
+    int decode_context_real(
+        uint8_t * apdu,
+        uint8_t tag_number,
+        float *real_value);
 
 /* from clause 20.2.7 Encoding of a Double Precision Real Number Value */
 /* and 20.2.1 General Rules for Encoding BACnet Tags */
@@ -196,6 +201,11 @@ extern "C" {
         uint8_t * apdu,
         uint8_t tag_number,
         double value);
+    BACNET_STACK_EXPORT
+    int decode_context_double(
+        uint8_t * apdu,
+        uint8_t tag_number,
+        double *double_value);
 
 /* from clause 20.2.14 Encoding of an Object Identifier Value */
 /* and 20.2.1 General Rules for Encoding BACnet Tags */